Constant radius dock leveler hinge

ABSTRACT

adapted to be disposed in a pit is disclosed. A hinge member with a hinge pin receiving area and a hinge pin disposed in the hinge member defines a center of rotation. A deck that is rotatable about the hinge pin includes a curved portion with a constant radius and a center of curvature substantially similar to the center of the hinge pin. The curved portion defines an elevation that remains constant as the deck rotates about the hinge pin.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/739,791 entitled “Constant Radius Dock Leveler Hinge,” filed Dec. 18,2003, currently pending, and incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a dock leveler system, and morespecifically to a rear hinge section of a dock leveler with a constantradius.

BACKGROUND OF THE DISCLOSURE

Dock levelers are often used to compensate for a height difference thatcan exist between a loading surface of a loading dock and the bed of atruck parked at the dock. A dock leveler system typically is mounted ina pit cut into the loading dock and includes a deck that is hinged atits back end to raise or lower the distal front end to generally matchthe height of the truck bed. A gap generally exists between the truckbed and the loading dock when the truck has backed up and is ready to beloaded or unloaded. An extension plate or lip can be pivotally coupledto the front end of the deck to bridge the gap. The deck and extendedlip provide a path for a forklift truck or the like to travel from theloading dock onto the truck bed, thus facilitating loading or unloadingof the truck.

If the bed of the truck is substantially at the same height as the floorof the loading dock, the deck elevation remains near a cross-trafficposition. If the bed of the truck is higher than the loading dock floor,the deck can be rotated upward into an above dock position. It the bedof the truck is lower than the loading dock floor, the deck can berotated into a below dock position. The deck can be used within a truckservice range which is generally defined as a ±10% grade (or ±6°angularity).

As can be seen in FIG. 1, a typical dock leveling system 10 is shown ina stored position in a loading dock 12 of a building. In the storedposition, also known as the cross-traffic position, the dock levelingsystem 10 is flush with the surrounding loading dock floor 13. The dockleveling system 10 is disposed in a pit 14 cut into the loading dock 12and includes a deck 16 and a frame structure 18. The dock levelingsystem 10 defines a path indicated by arrows 20 that a forklift travelsfrom the loading dock 12 into a truck to be loaded or unloaded. The deck16 has a front end 22 and a back end 24, and the back end 24 defines aback edge 26 that extends the width of the deck 16. The deck 16 isstrengthened by a plurality of stringers 28 that are approximatelyparallel to each other and run lengthwise from the front end 22 of thedeck 16 to the back end 24. Extending downward from the back end 24 ofthe deck 16 are a plurality of extension members 30, each of whichinclude a receiving hole 32. A deck 16 typically includes at least twopairs of extension members 30.

A lip 34 is connected to the front end 22 of the deck 16 by a lip hinge36. The lip 34 is rotatable from a pendant position shown in FIG. 1 inwhich the lip 34 hangs downward, to an extended position in which thelip 34 extends substantially coplanar to the deck 16 and is able spanthe gap between the loading dock 12 and the bed of a truck to beunloaded.

The frame structure 18 includes a plurality of vertical uprights 38 uponeach of which are disposed hinge members 40. The number of verticaluprights 38 generally corresponds to the number of pairs of extensionmembers 30. Each hinge member 40 includes a hinge pin 42 disposedtherethrough. Each hinge pin 42 also extends through a respectivereceiving hole 32 of one of the plurality of extension members 30,thereby rotatably connecting the deck 16 to the frame structure 18.

An upper member 41 is disposed on the hinge members 40. The upper member41 can be a piece of angle iron and extend the entire width of the dockloading system 10. The upper member 41 includes a leading edge 43opposite the back edge 26 of the deck 16.

Referring now to FIG. 2, the deck 16 is shown in the below-dockposition. In this position, the deck 16 has been rotated about the hingepins 42 so that the front end 22 of the deck 16 is lower than the backend 24. It is necessary to place the deck 16 in this position when thebed of a truck to be loaded or unloaded is lower than the floor of theloading dock 12.

As can be seen in FIG. 2, the back edge 26 of the back end 24 of thedeck 16 extends rearwardly of the center of the hinge pins 42. Thus,when the front end 22 of the deck 16 is lowered, the back end 24 of thedeck 16 is raised up a distance D1, thereby exposing the back edge 26and creating an above dock floor projection 44 in the path 20 of aforklift traveling from the dock floor to the bed of a truck. Travelingover the projection 44 can be an annoyance to the driver of the forkliftdue to the amount of times the driver must enter and depart the truck inloading. The projection 44 can also cause damage to the wheels of theforklift. Furthermore, if a user is wheeling a hand truck into and outof the truck bed, the projection 44 can be difficult to overcome andcause jostling of the boxes being moved. In other situations, operatorsmay be sliding skids along the ground into the truck. If an operatorslides a skid into the exposed back edge 26, the skid cannot ride overthe projection 44, and the skid can get damaged. This repeated impactcan lead to damage of the rear hinge 40 of the dock leveling system 10.

Referring now to FIG. 3, the deck 16 is depicted in the above-dockposition. In this example, the deck 16 can accommodate a truck that hasa bed that is higher than the floor 13 of the loading dock 12. The deck16 must then be rotated about the hinge pins 42 such that the front end22 of the deck 16 is raised above the level of the bed of the truck. Inthis example, a hydraulic cylinder 46 is shown that can aid in thelifting and/or lowering of the deck 16.

Again, because the back edge 26 of the deck 16 extends rearwardly of thecenter of the hinge pins 42, when the front end 22 of the deck 16 isrotated upward, the back edge 26 is rotated down a distance D2, thusexposing the leading edge 43 of the upper member 41 of frame structure18 and creating an above-deck projection 50 in the path 20 of theforklift. Again, when forklifts or skids exit towards the loading dock12, they impact the exposed leading edge 43 of the upper member 41,possibly causing damage to the forklift wheels or the skids.

Assuming that there is no projection when the dock leveling system 10 isin the stored position, the prior art has attempted to reduce theprojection 44 in the below dock position by changing the position ofhinge members 40. If the hinge members 40 are lowered, the distance D1will be lessened, and the projection 44 will be minimized. However, thiswill only exacerbate the projection 50 when the deck 16 is in theabove-dock position. Because the hinge members 40 are lowered, when thedeck 16 is in the above-dock position the distance D2 will be increasedby the amount the hinge members 40 are lowered. The converse is alsotrue in that if the hinge members 40 are raised, the projection 50 willbe minimized in the above-dock position, but the projection 44 will beincreased in the below dock position. Either approach does not produce asatisfactory solution.

For certain repairs to this type of dock leveler 10, the deck 16 can berotated upward so that a technician can enter the pit 14 under the deck16 and remove each of the individual hinge pins 42 from the extensionmembers 30. In this manner, the deck 16 can be removed from the framestructure 18 to provide greater accessibility if required.

Another type of known dock leveling system, known as a Edge-of-DockLeveler, or EOD, is depicted as structure 60 in FIG. 4. The EOD 60,described fully in U.S. Pat. No. 4,257,137, is fastened adjacent aloading dock 62 to the outside wall 64 of a building 66. The EOD 60includes a mounting plate 68 fastened to the outside wall 64. Themounting plate 68 is connected to a deck 70 by a first piano hinge 72.In the piano hinge 72, as is known, a series of short tubes 74 extendfrom the top of the mounting plate 68 and are interengaged with acomplementary series of short tubes 76 extending from the deck 70. Theinterengaged short tubes 74, 76 define a hollow tube that extends thewidth of the EOD 60. A rod (not shown) extends through the interengagedshort tubes 74, 76 the width of the EOD 60 to define the first pianohinge 72. A lip plate 78 is connected to the deck 70 by a second pianohinge 80.

Extending outward from the building 66 on either side of the EOD 60 is apair of bumper blocks 82. The bumper blocks 82 protect the building 66from a truck that is backing up to the loading dock 62. The deck 70 andlip plate 78 are sized such that when the truck backs against the bumperblocks 82, the lip plate 78 can extend out into the bed of the truck.

In this situation, the first piano hinge 72 does not create a projectionin the path of a forklift when the forklift is traveling into or out ofthe truck. However, due to the piano hinge construction and the bumperblocks 82 being placed on either side of the first piano hinge 72, therod inside the first piano hinge 72 cannot be removed. Accordingly, thedeck 70 cannot easily be removed to perform certain repairs orreplacement.

Accordingly, it would be beneficial to provide a dock leveling systemthat does not create a projection in the path of a forklift, and furtherprovides an easily removable deck for repair or replacement purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional side view of a prior art dock levelingsystem in the cross traffic position

FIG. 2 is a cross sectional side view of the dock leveling system ofFIG. 1 in the below dock position.

FIG. 3 is a cross sectional side view of second prior art dock levelingsystem in the above dock position.

FIG. 4 is a perspective view of an edge of dock prior art dock levelingsystem.

FIG. 5 is perspective view of a dock leveling system in the crosstraffic position constructed in accordance with the teachings of thisdisclosure.

FIG. 6 is a partial cross sectional view of the dock leveling system ofFIG. 5 taken along line 6-6.

FIG. 7 is a partial cross sectional view of the dock leveling system ofFIG. 5 taken along line 6-6 in the below dock position.

FIG. 8 is a partial cross sectional view of a second example of a dockleveling system constructed in accordance with the teachings of thisdisclosure.

FIG. 9 is a partial cross sectional view of the second example of thedock leveling system in the below dock position.

FIG. 10 is a partial cross sectional view of a third example of a dockleveling system constructed in accordance with the teachings of thisdisclosure.

FIG. 11 is a partial cross sectional view of the third example of thedock leveling system in the below dock position.

FIG. 12 is a partial cross sectional view of a fourth example of a dockleveling system constructed in accordance with the teachings of thisdisclosure.

While the disclosure is susceptible to various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit thedisclosure to the specific forms disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions, andthe equivalents falling within the spirit and scope of the invention asdefined by the appended claims.

DETAILED DESCRIPTION

Referring now to the drawings, four examples of a constant radius hingeassembly for a dock leveling system that provides a smooth transitionbetween the loading dock and the deck are depicted. The first example isdesignated by the reference numeral 140 and is shown in FIGS. 5, 6, and7. The second example is designated by the reference numeral 206 and isshown in FIGS. 8 and 9. The third example is designated by the referencenumeral 278 and is shown in FIGS. 10 and 11. Finally, the fourth exampleis designated by the reference numeral 338 and is shown in FIG. 12.Other examples are certainly possible and within the scope of thisdisclosure.

Referring now to FIGS. 5, 6, and 7, a first example of a dock levelingsystem 100 is disclosed. The dock leveling system 100 includes a frontside 102 and a back side 104 and has an overall length L and an overallwidth W. The front side 102 can be similar to prior art dock levelingsystems. The dock leveling system 100 includes a frame structure 106 anda deck 108 rotatably mounted to the frame structure 106. The dockleveling system 100 is disposed in a pit 110 cut into a loading dock 112of a building. The loading dock 112 has a dock floor 113.

FIG. 6 depicts the dock leveling system 100 in the cross-trafficposition, while FIG. 7 depicts the dock leveling system 100 in the belowdock position. The frame structure 106 includes a plurality of verticaluprights 114 extending upward from the base of the pit 110, only one ofthe vertical uprights 114 being shown in FIGS. 6 and 7. In one example,four vertical uprights 114 are spaced across the width W of the pit 110,but more or less vertical uprights 114 can be used depending on thewidth W of the dock leveling system 100 or its expected application. Onthe top of each vertical upright 114 is a hinge member 116. In thisexample, each hinge member 116 is a camel-back shaped portion of thevertical upright 114 and includes a receiving hole 118 (seen best inFIG. 12). A hinge pin 120 is rotatably disposed in each of the receivingholes 118 of the hinge members 116. Thus, a total of four individualhinge pins 120 are used in this example. The hinge pins 120 define acenter of rotation 122 for the deck 108 about the frame structure 106.

Disposed to the rear of the vertical uprights 114 is a rear transition124. The rear transition 124 can extend the full width W of the dockleveling system 100 and may serve as a point of attachment of the framestructure 106 to the dock floor 113. The rear transition 124, in thedepicted example, includes a V-support 126 and a plate 128. TheV-support 126 can be welded to the vertical uprights 114 and providessupport for the plate 128.

The plate 128 provides a surface for a forklift to traverse. The plate128 includes a front section 130 and a rear section 132. The frontsection 130 is directly supported by the V-support 126 and includes afront edge 134.

The rear section 132 is cantilevered out from the V-support 126. Therear section 132 can be cut and trimmed during installation of the dockleveling system 100. In some instances, the pit 110 may be cut too shortor may be out of square or alignment. In this instance, the rear section132 can be cut and trimmed on site such that the entire dock levelingsystem 100 can fit properly into the pit 110. In other examples, therear transition 124 can be omitted, and the vertical uprights 114 can bedisposed and attached against the wall of the pit 110.

The deck 108 includes a plate 136 that can extend the entire width W ofthe dock leveling system 100. The plate 136 provides the main surface onwhich a forklift may travel between the loading dock 112 and a truck.

The deck 108 also includes a plurality of stringers 138 extendingdownward from the plate 136. In a typical example, four or fivesubstantially equally spaced stringers 138 are used, however, more orless can be used depending on the application. The stringers 138 runlengthwise along the plate 136 generally parallel to each other from thefront side 102 towards the back side 104. The stringers 138 can have anycross-sectional shape along their length that is known to strengthen theplate 136. In this example, a C-channel is shown, however, other shapessuch as an L-beam or an I-beam can also be used.

The deck can be rotated about the hinge pins 120 from the cross trafficposition shown in FIG. 6 to the below dock position shown in FIG. 7, orto an above dock position not shown. In keeping with an aspect of thisinvention, the deck 108 includes a constant radius hinge assembly 140that pivotly connects the deck 108 to the vertical uprights 114. Theconstant radius hinge assembly 140 of this example ensures that as thedeck 108 is rotated up or down within its truck service range (again,±6° angularity) about the hinge members 116 to a below dock position orabove dock position, no edge is exposed and no projection is formed inthe path of a forklift.

The constant radius hinge assembly 140 includes a header 142 fastened tothe plate 136 and to the stringers 138. The header 142 includes a firstportion 144 that is generally curved, a second portion 146 that isgenerally horizontal, and a third portion 148 that generally extendsdownward. The header 142 can extend the entire width W of the deck 108,and form an extension of plate 136 to provide structural support for thedeck 108 towards the back side 104 of the dock leveling system 100. Thefirst portion 144 has a constant radius and a center of curvature thatis coincident with the center of rotation 122 of the hinge pins 120. Thesecond portion 146 of the header 142 extends generally in the same planeas the plate 136. The stringers 138 can each be welded to the thirddownward extending portion 148 of the header 142.

The first portion 144 defines a point of highest elevation 150 of theheader 142 when the deck 108 is in the cross-traffic position or in thebelow dock position. The point of highest elevation 150 defines anoverall elevation 152 of the hinge assembly 140 when the deck 108 is inthe cross traffic or below dock position. As will be understood, as thedeck 108 is rotated to the below dock position, the point of highestelevation 150 tracks along the surface of the first portion 144, andfurther the overall elevation 152 remains constant.

The deck 108 can include a plurality of header lugs 154 disposedunderneath the header 142, only one of which is shown in FIGS. 6 and 7.For each vertical upright 114, a header lug 154 can be disposed on eachside of the respective vertical upright 114. Thus, in this example,there are a total of eight header lugs 154.

Each header lug 154 can include a crown 156, a body 158, and a foot 160.The crown 156 is rounded and has a receiving hole 162. The crown 156 canbe welded to the first portion 144 of the header 142 and the foot 160can be welded to the third portion 148 of the header 142. The headerlugs 154 can be manufactured from ⅜″ plate steel or other size steelbased on the application. Accordingly, the header lugs 154 act tosupport the header 142.

The receiving holes 162 of each pair of header lugs 154 disposed onopposite sides of a vertical upright 114 encircle the respective singlehinge pin 120 disposed in the receiving hole 118 of the respectivevertical upright 114. In other words, the individual hinge pins 120disposed in each respective vertical upright 114 extend through thereceiving holes 162 of each pair of header lugs 154 disposed on oppositesides of the respective vertical upright 114, thereby forming the hingebetween the frame structure 106 and the deck 108. Thus, in this examplewith a total of four vertical uprights 114, a total of eight header lugs154 are used with a total of four hinge pins 120.

The hinge pins 120 can be free to rotate within the receiving holes 118,162. To lower friction, bearings or a lubricant could be inserted intothe receiving holes 118, 162. The hinge pins 120 can be held in place bya cotter pin or retaining clips or other structure known in the art.

The rear transition 124 defines an elevation 164 of the loading dock112. Again, the deck 108 defines an overall elevation 152 in the crosstraffic position. As the deck is lowered to the below dock position, theoverall elevation 152 of the deck 108 remains constant. This is due tothe first portion 144 of the header 142 having a constant radius and acenter of curvature coincident with the center of rotation 122 of thedeck 108. In this example, the overall elevation 152 of the deck 108 isapproximately equal to the elevation 164 of the rear transition 124, andthus the front edge 134 of the plate 128 of the rear transition 124 isnot exposed and no projection is created in the dock leveling system 100when the deck 108 is in the below dock position as in the prior art.

Moreover, the distance between the rear transition 124 and the hingeassembly 140 can be minimized in the present example. A gap is definedas the absolute distance D3 between the front edge 134 of the reartransition 124 and the first portion 144 of the header 142. Because thefirst portion 144 has a constant radius and a center of curvaturecoincident with the center of rotation 122 of the deck 108, the absolutedistance D3 remains constant through the lowering of the deck 108 to thebelow dock position. Further, because the front edge 134 of the plate128 is near a front edge 166 of the first portion 144 of the header 142,the absolute distance D3 will remain constant as the deck 108 is movedwithin its operating range of 60 in the above dock position.Accordingly, the absolute distance D3 between the deck 108 and the reartransition 124 can be maintained at a very small distance as not tocreate a projection or expose an edge in the path 20 of a forklift whilethe deck 108 is at either elevation or in the stored position.

A second example of a dock leveling system 180 disposed in a loadingdock 182 is shown in FIGS. 8 and 9 and also includes a constant radiushinge assembly that ensures that no edge is exposed or projection isformed in the path of a forklift when the deck is in any positionbetween the above dock and below dock truck service range.

The second example of the dock leveling system 180 includes a front side(not shown) and a back side 184. The front side can be similar to priorart dock leveling systems. The dock leveling system 180 includes a framestructure 186 and a deck 188 hingedly attached to the frame structure186.

The frame structure 186 for this example is similar to the firstexample. The frame structure 186 includes a plurality of verticaluprights 190, with a hinge member 192 disposed on each vertical upright190. Each hinge member 192 includes a receiving hole 194, and a hingepin 196 is disposed through each receiving hole 194. In this example,the deck 188 also includes a plate 198 and a plurality of stringers 200.Each stringer 200 has an end 202 and a side surface 204.

The deck 188 further includes a constant radius hinge assembly 206 thatensures that no projection or exposed edge is formed in the dockleveling assembly 180 when the deck 188 is within the truck servicerange in any position between the above dock position or the below dockposition. The constant radius hinge assembly 206 includes a header 208disposed along the width of the deck 188 that provides support to thedeck 188 similar to the first example. The header 208 includes a firstportion 210 that is curved and a second portion 212 that is generallyplanar. The first portion 210 is similar to the first portion 144 of thefirst example. The second portion 212 angles generally downward andincludes a plurality of slots (not shown), the number of which is equalto at least the number of stringers 200. The stringers 200 extend intothe slots of the second portion 212 of the header 208, such that eachstringer 200 is sandwiched within the slots of the header 208. Thestringers 200 and the header 208 are then welded together.

A header lug 214 can be disposed on each side of a respective verticalupright 190 as in the first example. Each header lug 214 includes acrown 216, a body 218, and a foot 220. However, in this example, eachfoot 220 and body 218 of the lugs 214 extend past each respective end202 of a stringer 200 and the side surface 204 of a respective stringer200. The second portion 212 of the header 208 is disposed directly onthe body 218 of each lug 214 for attachment of one to the other.

The frame structure 186 can include a rear transition 222 that definesan elevation 224. The first portion 210 of the header 208 defines apoint of highest elevation 226 for the constant radius hinge assembly206, and defines an overall height 228 for the constant radius hingeassembly 206.

In this example, the second portion 212 does not extend horizontally asin the first example, but extends generally angled downward. As such,the first portion 210 curves both down towards the back side 184 of thedock leveling assembly 180 as in the first example, but also the secondportion 212 curves down towards front side of the dock leveling assembly180.

As the deck 188 is rotated about a center of rotation 230 defined by thehinge pins 196, and is lowered to the below dock position, the overallelevation 228 of the deck 188 remains constant. This is due to the firstportion 210 of the header 208 having a constant radius and a center ofcurvature coincident with the center of rotation 230 of the deck 188. Inthis example, the overall elevation 228 of the constant radius hingeassembly 206 is approximately equal to the elevation 224 of the reartransition 222, and thus no projection is created and no edge is exposedin the dock leveling system 180 when the deck 188 is in the below dockposition.

Further, because the first portion 210 curves down toward the front ofthe dock leveling assembly 180, no projection is created when the deck188 is rotated to the above dock position. As will be understood, as thedeck 188 is rotated about the hinge pins 196, the point of highestelevation 226 for the constant radius hinge assembly 206 tracks alongthe first portion 210 towards the deck 188. Thus, the overall elevation228 of the hinge assembly 206 stays constant while the deck 188 isrotated to the above dock position as well.

Moreover, the distance between the rear transition 222 and the hingeassembly 206 can again be minimized in the present example. An absolutedistance D4 is defined as that distance between a front edge 232 of therear transition 222 and the first portion 210 of the header 208. Becausethe first portion 210 has a constant radius and a center of curvaturecoincident with the center of rotation 230 of the deck 188, the absolutedistance D4 remains constant through the lowering of the deck 188 to thebelow dock position and the raising of the deck to the above dockposition. Accordingly, the absolute distance D4 between the deck 188 andthe rear transition 222 can be maintained to a very small distance.

Thus, no projection or exposed edge is formed in the path of a forkliftwhile the deck 188 is in any position in the truck service range in abelow dock position or an above dock position. Further, the absolutedistance D4 between the header 208 and the rear transition 222 isconstant when the deck 188 is located within at least the truck servicerange.

A third example of a dock leveling system 250 disposed in a loading dock252 is shown in FIGS. 10 and 11 and also includes a constant radiushinge assembly that, like the previous two examples, ensures that noprojection or exposed edge is formed in the path of a forklift when thedeck is within the truck service range.

The dock leveling system 250 includes a front side (not shown) and aback side 254. The dock leveling system 250 includes a frame structure256 and a deck 258. The frame structure 256 includes a plurality ofvertical uprights 260 that each include a shoulder 262 extending towardsthe front side of the dock leveling system 250. The shoulder 262 definesa hinge member and includes a surface 264 that defines a hinge pinreceiving area. A hinge pin 266 is fixed in the hinge pin receiving area264 and defines a center of rotation 268 of the deck 258 about the framestructure 256. In this example, the hinge pin 266 can extend the fullwidth of the dock leveling system 250.

A rear transition 270 with a front edge 271 is affixed to the top of thevertical upright 260 and extends in the rear direction, cantilevered offthe vertical upright 260. A reinforcement member 272 depicted as anL-shape can be placed to help support the rear transition 270. The reartransition 270 can be trimmed as in the first example.

The deck 258 includes a plate 274 and a plurality of stringers 276extending down from the plate 274. The deck 258 further includes aconstant radius hinge assembly 278 that provides support to the deck 258similar to the previous examples. The hinge assembly 278 includes aheader 280 attached to a rear end 282 of the stringers 276. The header280 includes a curved portion 284, a first flat portion 286, and asecond flat portion 288 separated from the first flat portion 286 by thecurved portion 284. The header 280 wraps around the hinge pin 266 withthe curved portion 284 bearing directly on the hinge pin 266. The curvedportion 284 has a constant radius and a center of curvature that iscoincident with the center of rotation 268. This creates the hinge bywhich the deck 258 can rotate relative to the frame structure 256. Toreduce friction between the header 280 and the hinge pin 266, a bearing290 or bushing can be placed around the hinge pin 266.

The first flat portion 286 of the header 280 includes a plurality ofslots equal to at least the number of vertical uprights 260. Thevertical uprights 260 are disposed in the slots to allow the header 280to be disposed on and rotate about the hinge pin 266.

In this example, a lug need not be used. To ensure that the deck 258does not lift off the hinge pin 266 during use, a plurality of removablefasteners 292 are placed through suitable holes in the first flatportion 286, passing under the hinge pin 266, and through suitable holesthe second flat portion 288. This removably retains the deck 258 aboutthe hinge pin 266 and the frame structure 256.

An absolute distance D5 is defined as that distance between the frontedge 271 of the rear transition 270 and the curved portion 284 of theheader 280. The curved portion further defines a height 294 of theheader 280. The function of the constant radius hinge assembly 278 ofthe third example is similar to that of the second example. Thus, theheight 294 remains constant while the deck 258 is in any position in thetruck service range and no projection or exposed edge is formed in thepath of a forklift. Further, the absolute distance D5 between the header280 and the rear transition 270 is constant when the deck 258 is locatedwithin at least the truck service range.

A fourth example of a dock leveling system 300 disposed in a loadingdock 302 is shown in FIG. 12 and also includes a constant radius hingeassembly that ensures that no projection or exposed edge is formed inthe path of a forklift when the deck is in the truck service range.

The dock leveling system 300 includes a front side (not shown) and aback side 304. The dock leveling system 300 in this example alsoincludes a frame structure 306 and a deck 308. The frame structure 306in this example includes a plurality of vertical uprights 310 spacedalong the width of the dock leveling system 300. On top of each of thevertical uprights 310 is a hinge member 312. In this example, each hingemember 312 is in the shape of a camel back and includes a receiving hole314. A hinge pin 316 is disposed through the each receiving hole 314 asin the first two examples and defines a center of rotation 318 of thedeck 308 about the frame structure 306.

The deck 308 in this example includes a plate 320 and a plurality ofstringers 322 extending downward from the plate 320. The plate 320includes a first curved portion 324 and a flat portion 326. The curvedportion 324 extends towards the back side 304 off the stringers 322 andcurves downward. The curved portion 324 has a constant radius and has acenter of curvature coincident with the center of rotation 318.

A plurality of lugs 328 are disposed under the curved portion 324 of theplate 320. As in the previous examples, a lug 328 can be disposed oneach side of a respective vertical upright 310. Each lug 328 has a crown330 that is curved and can be welded to the bottom side of the curvedportion 324. Each crown 330 has a receiving hole 332 disposed thereinand receives the hinge pin 316. Each lug 328 can have a body 334 and afoot 336 and can be welded to the underside of plate 320 and/or thestringers 322.

In this example, the crown 330 of each of the lugs 328 is large enoughsuch that the crown 330 extends out past the periphery of the hingemember 312. Thus, the curved portion 324 does not contact the hingemember 312 through any portion of the rotation of the deck 308. In thisexample, the curved portion 324 of the plate 320 extending past thestringers 322 and the lugs 328 providing structural support for theplate 320 obviates the need for a header.

The vertical uprights 310 can include a shoulder 340. A support member342 in the shape of an L-bracket can be disposed along each of theshoulders 340 the width of the dock leveling system 300. A reartransition 344 with a leading edge 346 is disposed on the support member342.

The curved portion 324 of the deck 308 defines a constant radius hingeassembly 338 in the fourth example. The dock leveling system 300 issimilar to the dock leveling system 100 of the first example in that theconstant radius hinge assembly 338 forms no projection or exposed edgeis formed in the path of a forklift when the deck 308 is within thetruck service range, and a distance D6 between the curved portion 324and the leading edge 346 of the rear transition 344 remains constantwhen the deck 308 is in any position in the truck service range.

In addition to ensuring no projections or exposed edges are formed, thepresently disclosed examples further improve upon the prior art byfacilitating access and maintenance. More specifically, in each of theforegoing examples, the deck can be detached from the frame structure byrotating the deck upwards and removing the hinge pins from the hingemembers, or removing the retaining fasteners as disclosed in the thirdexample. The deck can then be removed and repairs or replacement caneasily be performed on both the deck and the frame structure.

From the foregoing, one of ordinary skill in the art will appreciatethat the present disclosure sets forth a constant radius hinge for adock leveling system. However, one of ordinary skill in the art couldreadily apply the novel teachings of this disclosure to any number ofhinged members. As such, the teachings of this disclosure shall not beconsidered to be limited to the specific examples disclosed herein, butto include all applications within the spirit and scope of theinvention.

1. A dock leveling system adapted to be disposed in a pit formed in aloading dock surface and adapted to provide a smooth transition betweenthe dock leveling system and the loading dock surface, the dock levelingsystem comprising: a deck rotatable about an axis of rotation between atleast a lowered position, in which the deck is declined relative tohorizontal, and an inclined position, in which the deck is inclinedrelative to horizontal; wherein the deck includes a plate and a headerdisposed adjacent to the plate, wherein the header has a curved portion.2. The system of claim 1, wherein the curved portion has a constantradius.
 3. The system of claim 1, wherein the curved portion has acenter of curvature substantially co-axial to the axis of rotation. 4.The system of claim 1, further comprising a gap defined between thecurved portion and an edge defined by the loading dock surface and aplane substantially perpendicular thereto, wherein the gap maintains aconstant dimension as the deck rotates.
 5. The system of claim 4,further comprising a rear transition that defines the edge.
 6. Thesystem of claim 1, further comprising a lug with a curved crown, andwherein the curved portion of the header is disposed on the crown of thelug.
 7. The system of claim 1, wherein the header includes a secondportion that is approximately co-planar with the plate.
 8. The system ofclaim 7, wherein the second portion is connected to an end of the plate.9. The system of claim 1, wherein the header includes a first portionand a second portion, and wherein the first portion and the secondportion are on opposite sides of the curved portion.
 10. The system ofclaim 1, further comprising a plurality of stringers extending down fromthe plate and extending into slots formed in the header.
 11. The systemof claim 1, wherein the plate is connected to the curved portion.
 12. Adock leveling system adapted to be disposed in a pit in a loading dockfloor and adapted to provide a smooth transition between the dockleveling system and the loading dock floor, the dock leveling systemcomprising: a pivotally-mounted deck with a curved portion, wherein thecurved portion is substantially tangential to a plane coplanar to theloading dock floor and wherein the curved portion remains substantiallytangential to the plane as the deck pivots; and a plurality of lugsfastened to the deck.
 13. The system of claim 12, wherein the pluralityof lugs are fastened to the curved portion of the deck.
 14. The systemof claim 12, wherein the curved portion has a constant radius.
 15. Thesystem of claim 12, wherein the curved portion has a center of curvaturesubstantially co-axial to an axis about which the deck pivots.
 16. Thesystem of claim 12, further comprising a gap defined between the curvedportion and an edge defined by the loading dock surface and a planesubstantially perpendicular thereto, wherein the gap maintains aconstant dimension as the deck rotates about the hinge pin.
 17. Thesystem of claim 16, further comprising a rear transition that definesthe edge.
 18. The system of claim 12, wherein the deck comprises a plateand a header, wherein the header defines the curved portion.
 19. Thesystem of claim 18, wherein the header includes a second portion that isapproximately co-planar with the plate.
 20. The system of claim 19,wherein the second portion is connected to an end of the plate.
 21. Thesystem of claim 18, wherein the header includes a first portion and asecond portion, and wherein the first portion and the second portion areon opposite sides of the curved portion.
 22. The system of claim 18,wherein the plate is connected to the curved portion.
 23. A dockleveling system adapted to be disposed in a pit formed in a loading dockfloor, the dock leveling system comprising: a deck rotatable between atleast a lowered position, in which the deck is declined relative to theloading dock floor, and a raised position, in which the deck is inclinedrelative to the loading dock floor; wherein the deck includes a platehaving an upper surface and a header disposed adjacent to the plate,wherein the header forms an extension of the upper plate surface and theheader is adapted to help provide structural support for the deck. 24.The system of claim 23, wherein the header has a curved portion with aconstant radius and a center of curvature substantially co-axial to anaxis about which the deck rotates.
 25. A rear header for a pit-styledock leveler intended to help provide a smoother transition between aloading dock surface and the dock leveler, the dock leveler including adeck with a plate, the deck being rotatable about an axis of rotation,the rear header comprising: a structural member adapted to be coupled tothe deck adjacent the plate to form an extension thereof, wherein thestructural member includes a curved portion.
 26. The rear header ofclaim 25, wherein the curved portion has a constant radius with a centerof curvature that is substantially co-axial to the axis of rotation. 27.A dock leveler adapted to be disposed in a pit formed in a loading docksurface, the dock leveler comprising: a deck rotatable about an axis ofrotation, wherein the deck includes a plate and a header disposedadjacent to the plate, wherein the header has a curved portion adaptedto help to provide a smooth transition between the loading dock surfaceand the deck; and an extension lip pivotally coupled to the deck. 28.The dock leveler of claim 27, wherein the curved portion has a constantradius.
 29. The dock leveler of claim 27, wherein the curved portion hasa center of curvature substantially co-axial to the axis of rotation.30. A dock leveler adapted to move between a stored position, aninclined position, and a declined position, the dock leveler adapted tobe disposed in a pit formed in a loading dock surface, and the dockleveler adapted to minimize any projection of the leveler above theloading dock surface when the dock leveler is in the declined position,the dock leveler comprising: a deck rotatable about an axis of rotation,wherein the deck includes a plate and a header disposed adjacent to theplate, wherein the header has a curved portion that is substantiallytangential to the plate.
 31. The dock leveler of claim 30, wherein thecurved portion has a constant radius.
 32. The dock leveler of claim 30,wherein the curved portion has a center of curvature substantiallyco-axial to the axis of rotation.